The long-term objective of this project is to determine, at atomic resolution, the crystal structure of Band 3, the anion transport protein of the human erythrocyte membrane. These studies are necessary if we are to understand the mechanism of anion transport at the molecular level. The specific aims of this two year grant are: (1) to characterize the structure of purified Band 3 in detergent solutions using various hydrodynamic and spectroscopic techniques, and (2) to produce crystals of Band 3 and its major domains that are suitable for X-ray diffraction studies. This research is important for a number of reasons. Firstly, little is known about the structure of membrane proteins. Secondly, the mechanism by which transport proteins move substrates across biological membranes is unknown. Thirdly, diseases such as cystic fibrosis may be the result of a defect in a transport process. Band 3 is an ideal candidate for crystallography since it can be readily purified, its sequence (murine) is known and a great deal of information is available concerning its structure and function.